This is a first impression without even considering the plot/writing, or actors/voices, or even the competition at the box office.
Hate to disagree, but Titan AE and Spirit are two examples that contradict your observation. Both of my kids loved those films and they're good enough that I haven't minded sitting through them a few times.
Fwiw, Titan AE didn't do well at the box office, but it was still a pretty slick film (kinda what I'm guessing Treasure Planet was hoping to emulate - in terms of production quality). Instead it sounds like it's doomed to the same lack of box office success).